Granules are a suitable form for medicaments which are to be administered orally. A dose of medicament in the form of granules may be measured and administered by incorporating into a sachet or using a spoon or may be incorporated into a capsule of formulated into a tablet to be swallowed. It is preferred that such granules are of regular shape and substantially spherical to give good fluidity for ease of dispensing and capsule filling or tabletting as well as for aesthetic appeal. Spherical granules are also easier to coat with taste masking, enteric/protective and sustained release coating materials.
At present, there are two methods of preparing spherical granules. One is to extrude a cylindrical granule using a "squeeze-out" type granulation machine and then to make it spherical in shape by using a marumeriser, a machine which "cuts off the edges" of the cylinder shape. This method involves difficult manufacturing conditions and is time consuming which precludes its routine use. The other method used is to gradually coat a core particle such as granulated sugar using a centrifugal flow type granulator but this is a time consuming process and is not generally applicable to a wide range of medicaments where the proportion of the volume of the medicament in the granules high (20% or higher).
The most efficient method of preparing granules is using a high-speed agitation granulator machine which mixes and granulates in one operation using two rotating blades, a main blade with a horizontal plane of rotation and a chopper blade above it with a vertical plane of rotation (cross blade). The medicament and excipients are introduced into the machine in advance and binder solution is then poured or sprayed into the machine from above whilst the blades are rotating. By this method, granules can be prepared quickly and easily but the disadvantage is that the resulting granules are irregular and non-spherical in shape and do not have the advantages associated with spherical granules.
Surprisingly, we have now discovered a method of preparing substantially spherical granules using a high-speed agitation granulator machine thus avoiding the need to use the "squeeze-out" and marumerizer method.